As a thin, high image quality, and low power consumption display device, an organic EL display device is known. In the organic EL display device, a plurality of pixel circuits are arranged in a matrix form, each including an organic EL element, which is a current-driven self-luminous type electro-optic element, and a driving transistor.
As the driving transistor, typically, a thin-film transistor (hereinafter, occasionally abbreviated as “TFT”) is used, and a characteristic of the TFT tends to easily vary. Such a variation in a characteristic of the driving transistor may cause a brightness variation. The “characteristic of the driving transistor” referred here is a threshold voltage and mobility of the driving transistor, for example.
Conventionally, various organic EL display devices that compensate for a characteristic variation of a driving transistor have been known. Patent Document 1 discloses an organic EL display device that compensates for a variation in the threshold voltage of the driving transistor, by providing in the pixel circuit a transistor that detects a variation in the threshold voltage. Hereinafter, compensating for a variation in the threshold voltage will be occasionally called “threshold voltage compensation”. Patent Document 2 discloses an organic EL display device that performs threshold voltage compensation, by providing at the outside of the pixel circuit a circuit that detects the threshold voltage of the driving transistor and that supplies to a data line a voltage corrected based on a result of the detection. Patent Document 3 discloses an organic EL display device that compensates for a characteristic variation of the driving transistor by detecting a driving current which flows to the driving transistor and by controlling a voltage supplied to a data line based on a result of the detection. Patent Document 4 discloses an organic EL display device that compensates for a characteristic variation of the driving transistor by holding, in a memory, characteristic variation information of the driving transistor and by correcting a voltage supplied to a data line, based on the variation information read from the memory.